PROJECT SUMMARY/ABSTRACT By some estimates, femoroacetabular impingement syndrome (FAIS) accounts for 82% of hip osteoarthritis cases. Patients present with loss of femoral head sphericity, reduction in femoral-neck offset, and/or an excessively prominent acetabular wall, and report position- or motion-related pain. The theory of FAIS pathophysiology is that pathoanatomy causes pathomechanics. However, quantitative understanding of this disease is lacking. Few investigators have analyzed the relationship between hip anatomy and biomechanics in FAIS patients; those that have relied on 2D measures that incompletely describe hip shape. Based on these 2D shape metrics, ~35% of the general population carries a ?silent? form of the disease, which has hindered progress to understand why FAI morphology causes damage. To advance understanding of FAIS pathophysiology, a cross-sectional study of FAIS patients and controls will be performed. Aim 1 will quantify pathomorphology of FAIS. Hip anatomy will be visualized and compared using statistical shape modeling (SSM). Notably, SSM compares shape over the 3D continuum, rather than relative to a single, 2D image. The central hypothesize is that SSM will detect differences in 3D shape of symptomatic and asymptomatic hips; further, this difference will occur whether controls are analyzed together or as anatomic subgroups identified via cluster analysis. Aim 1 will improve clinical understanding of this disease and inform development of better techniques to evaluate hip anatomy. Aim 2 will quantify pathokinematics of FAIS. Hip motion will be measured during functional activities in FAIS patients and controls. The central hypothesis is that hip kinematics will differ between FAIS patients and controls and that significant relationships exist between hip shape and hip kinematics; further, controls with hip shape similar to FAIS patients will have altered kinematics compared to controls that do not. Aim 2 will guide development of treatment options through a better understanding of compensatory mechanisms that occur across groups. The training plan is tailored to facilitate achievement of the applicant?s career goals through development of scientific and professional skills and opportunities to generate and disseminate research findings. The training plan enables collaboration between the applicant and sponsors in the University of Utah Departments of Orthopaedics and Physical Therapy, and Scientific Computing and Imaging Institute. The sponsor team (Drs. Andrew Anderson (primary mentor), Shireen Elhabian, Kenneth ?Bo? Foreman, Stephen Aoki) is well-qualified to train the applicant in computational biomechanics, analysis techniques for high-dimensional data, motion analysis, and clinical treatment of hip pathology. The sponsor team has a strong history of successful collaboration, mentorship, publication, and funding. Receipt of an F32 fellowship will enhance synergy between the applicant and sponsors, enable the applicant to take full advantage of the strong research, clinical, and educational environment at the University of Utah, and ensure the applicant success in becoming an independent, impactful researcher.